smbd: avoid become_user_without_service() in close_directory()

smbd: avoid become_user_without_service() in close_directory()

Here we called become_user_without_service() just in order to be able to fetch
the nt_token and unix_token subsequently via get_current_[nt|u]tok(conn). The
same can be achieved by fetching the session_info with
smbXsrv_session_info_lookup().

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>